System and method for extracting lithium from salt lake

Abstract

The invention provides a salt lake lithium extraction system and method.The system comprises a multi-stage counter-current extraction mechanism, a washing mechanism and a reverse extraction mechanism which are sequentially arranged in the flow direction of an extraction agent, and the multi-stage counter-current extraction mechanism comprises two or more than two sets of multi-stage extraction tanks which are arranged in parallel; each group of multi-stage extraction tanks comprises a first-stage extraction tank, a second-stage extraction tank,..., and an n-stage extraction tank which are connected in series, each n-stage extraction tank is connected with a storage tank for brine to be extracted, and each first-stage extraction tank is connected with an extraction agent storage tank; each n-stage extraction tank is connected with a washing mechanism, a washing liquid input pipe is arranged on one side, far away from the extraction tanks, of the washing mechanism, and the other side, far away from the extraction tanks, of the washing mechanism is further connected with a reverse extraction mechanism; a back extraction liquid input pipe is arranged on one side, far away from the washing mechanism, of the back extraction mechanism, and a high-lithium liquid storage tank is arranged on one side, close to the washing mechanism, of the back extraction mechanism; according to the method, the defects of slow phase splitting and long time consumption of the extraction section are reasonably optimized, and the extraction efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium extraction, and in particular to a system and method for extracting lithium from a salt lake. Background Art

[0002] With the rapid development of new energy vehicles and energy storage industries, the global demand for lithium resources has exploded. As the main form of global lithium resources, the development efficiency of salt lake brine directly affects the security of lithium resource supply.

[0003] The existing salt lake lithium extraction technology has the following main problems: First, for high magnesium-lithium ratio (Mg 2+ / Li⁺>50) salt lake system, the traditional adsorption method has the problems of low adsorption capacity, limited selectivity, large desorbent consumption, and high-performance adsorbents are expensive and have limited service life; secondly, membrane separation technology faces technical difficulties such as rapid membrane flux attenuation and poor anti-pollution ability in actual application, which limits the improvement of lithium extraction efficiency and cost control in salt lakes.

[0004] Solvent extraction is widely used in the field of lithium recovery from lithium batteries because of its high separation efficiency, low energy consumption and lower energy requirements than traditional processes. After disassembly and acid leaching, lithium batteries are acidic and the lithium ion content is usually around 5g / L, which is relatively high and convenient for subsequent extraction. The brine in salt lakes has a low lithium concentration, so the lithium ion content of the old brine after potassium precipitation is around 0.1~0.5g / L, and the lithium ion content in the lithium precipitation mother liquor is generally 1.2~2g / L.

[0005] Lithium extraction by extraction generally adopts centrifugal extraction or box extraction. Centrifugal extraction has high separation efficiency, but it is not suitable for extraction of salt lake brine with large flux. Box extraction is not affected by centrifugal speed and capacity, so it can process salt lake brine with large flux (a single extraction tank can process thousands of tons per day), but it is limited by phase separation time, resulting in low extraction efficiency.

[0006] Therefore, it is urgent to develop a new salt lake lithium extraction system to achieve efficient development of large-flux salt lake brine. Summary of the invention

[0007] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a system and method for extracting lithium from salt lakes, so as to solve the problem of low extraction flux in the prior art.

[0008] To achieve the above-mentioned and other related purposes, the present invention provides a system for extracting lithium from a salt lake, the system comprising a multi-stage countercurrent extraction mechanism, a washing mechanism and a stripping mechanism sequentially arranged along the flow direction of the extractant; The multi-stage countercurrent extraction mechanism comprises two or more groups of multi-stage extraction tanks arranged in parallel, each group of the multi-stage extraction tanks comprises a primary extraction tank, a secondary extraction tank, ..., an n-stage extraction tank arranged in series, each of the n-stage extraction tanks is respectively connected to a brine storage tank to be extracted, and each of the primary extraction tanks is respectively connected to an extractant storage tank; Each of the n-stage extraction tanks is connected to the washing mechanism, a washing liquid input pipe is provided on the side of the washing mechanism away from the extraction tank, and the side of the washing mechanism away from the extraction tank is also connected to the stripping mechanism; A stripping liquid inlet pipe is arranged on the side of the stripping mechanism away from the washing mechanism, and a high-lithium liquid storage tank is arranged on the side of the stripping mechanism close to the washing mechanism.

[0009] Preferably, the washing mechanism comprises at least a primary washing tank and a secondary washing tank arranged in series, the oil phase outlet of each of the n-stage extraction tanks is connected to the oil phase inlet of the primary washing tank, the secondary washing tank is connected to the washing liquid storage tank via the washing liquid input pipe, and the oil phase outlet of the secondary washing tank is connected to the stripping mechanism.

[0010] Preferably, the stripping mechanism comprises a primary stripping tank, a secondary stripping tank and a tertiary stripping tank which are sequentially arranged in series, the primary stripping tank being connected to the high lithium liquid storage tank and the oil phase outlet of the secondary washing tank respectively, and the tertiary stripping tank being connected to the stripping liquid storage tank via a stripping liquid input pipe.

[0011] Preferably, each of the primary extraction tanks is also connected to a raffinate clarification tank, and the oil phase outlet of the raffinate clarification tank is connected to the inlet of the extractant storage tank, so that the extractant remaining in the raffinate can be recovered.

[0012] The present invention also provides a method for extracting lithium from a salt lake using the system for extracting lithium from a salt lake as described above, comprising the following steps: S1, the extract is respectively fed from each of the first-stage extraction tanks into the multi-stage countercurrent extraction mechanism, the brine to be extracted is respectively fed from each of the n-stage extraction tanks into the multi-stage countercurrent extraction mechanism, the raffinate discharged from each of the n-stage extraction tanks is respectively fed into the extraction tank of the previous stage, and finally the raffinate is discharged from each of the first-stage extraction tanks, and each of the n-stage extraction tanks obtains the extracted oil phase; S2, the extracted oil phase obtained in step S1 enters a washing mechanism and is washed with a washing liquid to obtain a washed oil phase; S3. The washed oil phase obtained in step S2 enters a stripping mechanism and is stripped using a stripping liquid to obtain a high-lithium solution.

[0013] As described above, the system and method for extracting lithium from salt lakes of the present invention have the following beneficial effects: The salt lake lithium extraction system of the present invention adopts a multi-stage countercurrent extraction mechanism arranged in parallel, which reasonably optimizes the shortcomings of slow phase separation and long time in the extraction stage, improves the extraction efficiency, and then obtains a high-lithium liquid through a washing mechanism and a stripping mechanism in sequence. Furthermore, the washing residue obtained by the washing mechanism enters the multi-stage countercurrent extraction mechanism again for extraction, and the oil phase in the raffinate clarification tank also enters the multi-stage countercurrent extraction mechanism again for extraction, thereby improving the extraction rate of lithium; the oil phase discharged from the three-stage stripping tank returns to the multi-stage countercurrent extraction mechanism, so that the extractant is reused and the consumption of the extractant is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the structure of the system for extracting lithium from salt lakes of the present invention.

[0015] Description of Figure Numbers 100 Multi-stage countercurrent extraction mechanism 200 Washing mechanism 300 Anti-extraction agency 400 Raffinate clarification tank 500 First oil separator 600 Second oil separator 101 Extractant storage tank 102 Brine storage tank to be extracted 11 Primary extraction tank 12 Secondary extraction tank 13 n-stage extraction tank 201 Washing liquid storage tank 21 Primary washing tank 22 Secondary washing tank 301 Stripping liquid storage tank 302 High lithium liquid storage tank 31 Primary stripping tank 32 Secondary stripping tank 33 Three-stage stripping tank DETAILED DESCRIPTION

[0016] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0017] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0018] In the present invention, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.

[0019] When a numerical range is disclosed herein, the above range is deemed to be continuous and includes the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all sub-ranges included therein. For example, a specified range from "1 to 10" should be deemed to include any and all sub-ranges between a minimum of 1 and a maximum of 10. Exemplary sub-ranges of ranges 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0020] In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before or after the combination step or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified; and, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the present invention without substantially changing the technical content.

[0021] The inventors found in the experiment that the box-type extraction process requires a large mother liquor flow rate and an extract flow rate, and the water-oil phase flow ratio is generally about 1:1. In the washing section and the stripping section, due to the use of acid washing, the washing section generally uses 1-2 mol / L of acid for washing, and the stripping section uses 3-6 mol / L of acid for stripping. The flow rates of the washing liquid and the stripping liquid are relatively small, and the water-oil phase flow ratio is about 1:15. In addition, the phase separation is faster under acidic conditions, so the phase separation time and the mother liquor flow rate of the extraction section limit the overall extraction efficiency.

[0022] In view of this, the first aspect of the present invention provides a system for extracting lithium from a salt lake, the system comprising a multi-stage countercurrent extraction mechanism 100, a washing mechanism 200 and a stripping mechanism 300 arranged in sequence along the flow direction of the extractant; The multi-stage countercurrent extraction mechanism 100 comprises two or more groups of multi-stage extraction tanks arranged in parallel, each group of the multi-stage extraction tanks comprises a primary extraction tank 11, a secondary extraction tank 12, ..., an n-stage extraction tank 13 arranged in series, each of the n-stage extraction tanks 13 is respectively connected to a brine storage tank 102 to be extracted, and each of the primary extraction tanks 11 is respectively connected to an extractant storage tank 101; Each of the n-stage extraction tanks 13 is connected to the washing mechanism 200. A washing liquid input pipe is provided on the side of the washing mechanism 200 away from the extraction tank. The side of the washing mechanism 200 away from the extraction tank is also connected to the stripping mechanism 300. A stripping liquid inlet pipe is disposed on a side of the stripping mechanism 300 away from the washing mechanism 200 , and a high-lithium liquid storage tank 302 is disposed on a side of the stripping mechanism 300 close to the washing mechanism 200 .

[0023] In a preferred embodiment of the present invention, n≤5.

[0024] In the system for extracting lithium from salt lakes of the present invention, the washing mechanism 200 comprises at least a primary washing tank 21 and a secondary washing tank 22 arranged in series, the oil phase outlets of each of the n-stage extraction tanks 13 are connected to the oil phase inlet of the primary washing tank 21, the secondary washing tank 22 is connected to the washing liquid storage tank 201 through the washing liquid input pipe, and the oil phase outlet of the secondary washing tank 22 is connected to the stripping mechanism 300. The washing tanks in the washing mechanism 200 can be arranged in multiple stages, at least two stages.

[0025] In the system for extracting lithium from salt lakes of the present invention, the water phase outlet of the primary washing tank 21 is connected to the inlet of each of the n-stage extraction tanks 13, so that the residual liquid obtained by the primary washing tank 21 is extracted again. In the present invention, the water phase in the primary washing tank 21 is returned to the n-stage extraction tank 13 again, and part of the washed lithium is recovered again.

[0026] In the system for extracting lithium from salt lakes of the present invention, the stripping mechanism includes a primary stripping tank 31, a secondary stripping tank 32 and a tertiary stripping tank 33 which are sequentially arranged in series, the primary stripping tank 31 is respectively connected to the high lithium liquid storage tank 302 and the oil phase outlet of the secondary washing tank 22, and the tertiary stripping tank 33 is connected to the stripping liquid storage tank 301 through a stripping liquid input pipe.

[0027] In the system for extracting lithium from salt lakes of the present invention, the oil phase outlet of the tertiary stripping tank 33 is also connected to the extractant storage tank 101, so that the oil phase after stripping can be used again for the brine to be extracted.

[0028] In the system for extracting lithium from salt lakes of the present invention, each of the primary extraction tanks 11 is also connected to a raffinate clarification tank 400, and the oil phase outlet of the raffinate clarification tank 400 is connected to the inlet of the extractant storage tank 101, so that the extractant remaining in the raffinate can be recovered.

[0029] In the system for extracting lithium from salt lakes of the present invention, the raffinate clarification tank 400 is also connected to the first oil separator 500. The raffinate discharged from the raffinate clarification tank 400 enters the first oil separator 500 for further oil removal.

[0030] In the salt lake lithium extraction system of the present invention, the high-lithium liquid storage tank 302 is also connected to a second oil separator 600 to remove oil from the obtained high-lithium liquid.

[0031] A second aspect of the present invention provides a method for extracting lithium from a salt lake using the system for extracting lithium from a salt lake as described above, comprising the following steps: S1, the extract is respectively fed from each of the first-stage extraction tanks 11 into the multi-stage countercurrent extraction mechanism 100, the brine to be extracted is respectively fed from each of the n-stage extraction tanks 13 into the multi-stage countercurrent extraction mechanism 100, the raffinate discharged from each of the n-stage extraction tanks 13 is respectively fed into the extraction tank of the previous stage, and finally the raffinate is discharged from each of the first-stage extraction tanks 11, and each of the n-stage extraction tanks 13 obtains the extracted oil phase; S2, the extracted oil phase obtained in step S1 enters the washing mechanism 200 and is washed with a washing liquid to obtain a washed oil phase; S3. The washed oil phase obtained in step S2 enters the stripping mechanism 300, and is stripped using a stripping liquid to obtain a high-lithium solution.

[0032] In the method for extracting lithium from a salt lake of the present invention, the brine to be extracted in step S1 is salt lake brine after precipitation and filtration; the concentrations of the ions in the brine to be extracted used in step S1 are a carbonate ion concentration of 6-10 g / L, a lithium ion concentration of 1.2-1.8 g / L, a sodium ion concentration of 45-60 g / L, a chloride ion concentration of 60-90 g / L, and calcium ion and magnesium ion concentrations of less than 5 ppm.

[0033] In the method for extracting lithium from a salt lake of the present invention, in step S2, a washing residue is obtained after the washing, and the washing residue is returned to the n-stage extraction tank 13.

[0034] In the method for extracting lithium from a salt lake of the present invention, in step S3, an oil phase liquid is obtained after the stripping, and the oil phase liquid is returned to the extractant storage tank 101 or the primary extraction tank 11.

[0035] The extract in step S1 is a diketone compound, and specifically can be the extractant disclosed in Example 1 of patent publication number CN 118241039 A.

[0036] In some embodiments of the present invention, the washing liquid in step S2 is a 0.5-2.5 mol / L acid solution, for example, 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L or 2.5 mol / L.

[0037] In some embodiments of the present invention, the stripping solution in step S3 is a 3-6 mol / L acid solution, for example, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L or 6 mol / L.

[0038] Example 1 This embodiment provides a system and method for extracting lithium from a salt lake. Figure 1 As shown, the system includes a multi-stage countercurrent extraction mechanism 100, a washing mechanism 200 and a stripping mechanism 300 which are sequentially arranged along the flow direction of the extractant; The multi-stage countercurrent extraction mechanism 100 includes two groups of multi-stage extraction tanks arranged in parallel, and n=3, that is, each group of the multi-stage extraction tanks includes a primary extraction tank 11, a secondary extraction tank 12, and a tertiary extraction tank arranged in series, each of the tertiary extraction tanks is respectively connected to the brine storage tank 102 to be extracted, and each of the primary extraction tanks 11 is respectively connected to the extractant storage tank 101; each of the primary extraction tanks 11 is also connected to a raffinate clarification tank 400, the oil phase outlet of the raffinate clarification tank 400 is connected to the inlet of the extractant storage tank 101, the raffinate clarification tank 400 is also connected to a first oil separator 500, the oil phase outlet of the raffinate clarification tank 400 is connected to the tertiary extraction tank, and the raffinate clarification tank 400 is also connected to the first oil separator 500; Each of the three-stage extraction tanks is connected to the washing mechanism 200, and the washing mechanism 200 includes a primary washing tank 21 and a secondary washing tank 22 arranged in series, the oil phase outlet of each of the three-stage extraction tanks is connected to the oil phase inlet of the primary washing tank 21, the water phase outlet of the primary washing tank 21 is respectively connected to the inlet of each of the three-stage extraction tanks, the secondary washing tank 22 is connected to the washing liquid storage tank 201 through the washing liquid input pipe, and the secondary washing tank 22 is also connected to the stripping mechanism 300; The stripping mechanism 300 includes a primary stripping tank 31, a secondary stripping tank 32 and a tertiary stripping tank 33 which are arranged in series, wherein the primary stripping tank 31 is respectively connected to the high lithium liquid storage tank 302 and the oil phase outlet of the secondary washing tank 22, the tertiary stripping tank 33 is connected to the stripping liquid storage tank 301, and the oil phase outlet of the tertiary stripping tank 33 is also connected to the extractant storage tank 101; the high lithium liquid storage tank 302 is also connected to the second oil separator 600.

[0039] The concentrations of various ions in the brine to be extracted are: carbonate ion concentration is 10g / L, lithium ion concentration is 1.8g / L, sodium ion concentration is 60g / L, chloride ion concentration is 80g / L, and calcium ion and magnesium ion concentrations are both less than 5ppm.

[0040] The washing liquid is: 1.5 mol / L hydrochloric acid solution.

[0041] The stripping solution is: 5mol / L hydrochloric acid solution.

[0042] The specifications of the extraction tank (diameter × height): Φ2m × 2.5m, the specifications of the raffinate clarification tank (length × width × depth): 10m × 4m × 1m.

[0043] The method for extracting lithium from a salt lake comprises the following steps: S1, the extracts are respectively fed from each of the first-stage extraction tanks into the multi-stage countercurrent extraction mechanism, and the flow rate of each group of extracts is 25 m 3 / h; the brine to be extracted enters the multi-stage countercurrent extraction mechanism from each of the three-stage extraction tanks, and the feed flow rate of each group of brine to be extracted is 30 m 3 / h; the raffinate discharged from each of the three-stage extraction tanks enters the extraction tank of the previous stage respectively, and finally the raffinate is discharged from each of the first-stage extraction tanks to the raffinate clarification tank, the oil phase clarified and floated in the raffinate clarification tank is returned to the extractant storage tank for recovery, the raffinate in the raffinate clarification tank enters the oil separator for further oil removal, and each of the three-stage extraction tanks obtains the extracted oil phase; S2: The extracted oil phase obtained in step S1 enters the primary washing tank, and the washing liquid enters the washing mechanism from the secondary washing tank from the washing liquid storage tank. The flow rate of the washing liquid is 2.8 m 3 / h; the water phase obtained after washing enters the third-stage extraction tank again from the first-stage washing tank for stripping, and the oil phase obtained after washing enters the stripping mechanism; S3: The washed oil phase obtained in step S2 enters the primary stripping tank, and the stripping liquid enters the stripping mechanism from the stripping liquid storage tank through the tertiary stripping tank. The flow rate of the stripping liquid is 3.2 m 3 / h, lithium concentration 33.2g / L. The oil phase obtained after stripping returns to the extractant storage tank for re-extraction, and the water phase obtained after stripping enters the high lithium liquid storage tank and then passes through the second oil separator for further oil removal to obtain high lithium liquid.

[0044] Example 2 Compared with Example 1, the multi-stage countercurrent extraction mechanism 100 includes three groups of multi-stage extraction tanks arranged in parallel, and n=3, that is, each group is three-stage extraction tanks connected in series, and the flow rate of each group of extracts is 20 m 3 / h, the feed flow rate of each group of brine to be extracted is 25 m 3 / h; the washing mechanism 200 includes two washing tanks connected in series, and the washing liquid flow rate is 4.2 m 3 / h; the stripping mechanism 300 includes three stripping tanks connected in series, and the stripping liquid flow rate is 4 m 3 / h. The rest is the same as in Example 1.

[0045] Comparative Example 1 Compared with Example 1, the multi-stage countercurrent extraction mechanism 100 is not arranged in parallel, but only has three stages of extraction tanks connected in series, and the flow rate of each group of extraction liquid is 25 m 3 / h, the feed flow rate of each group of brine to be extracted is 30 m 3 / h; the washing mechanism 200 includes two washing tanks connected in series, and the washing liquid flow rate is 1.5 m 3 / h; the stripping mechanism 300 includes three stripping tanks connected in series, and the stripping liquid flow rate is 1.65 m 3 / h. The rest is the same as in Example 1.

[0046] Comparative Example 2 Compared with Example 1, the multi-stage countercurrent extraction mechanism 100 includes two sets of extraction tanks arranged in parallel, but n=1, that is, only one extraction tank is arranged in each set, and the flow rate of the extract in each set is 35 m 3 / h, the feed flow rate of each group of brine to be extracted is 30m 3 / h; the washing mechanism 200 includes two washing tanks connected in series, and the washing liquid flow rate is 3.6 m 3 / h; the stripping mechanism 300 includes three stripping tanks connected in series, and the stripping liquid flow rate is 2.9 m 3 / h. The rest is the same as in Example 1.

[0047] The high lithium solution obtained in the above examples and comparative examples was tested, and the results are shown in Table 1.

[0048] Table 1 <![CDATA[12-hour brine input volume (m 3 ).]]> <![CDATA[Volume of high-lithium liquid obtained in 12 hours (m 3 )]]> High lithium solution concentration (g / L) Comprehensive lithium yield (%) Example 1 720 38.4 33.2 98.37 Example 2 900 48 32.3 95.70 Comparative Example 1 360 19.8 32.1 98.08 Comparative Example 2 720 34.8 31.5 84.58 From the data in Table 1, it can be seen that Example 1 adopts two sets of parallel three-stage extraction methods, and the lithium liquid output is nearly doubled compared with Comparative Example 1. Example 2 adopts a three-parallel extraction method with the highest output, but the stripping yield will be reduced, which will reduce the comprehensive lithium yield. Comparative Example 2 adopts two sets of parallel one-stage extraction methods, and the extraction rate will be reduced, resulting in a lower comprehensive lithium yield.

[0049] Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0050] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A system for extracting lithium from a salt lake, characterized in that: The system comprises a multi-stage countercurrent extraction mechanism (100), a washing mechanism (200) and a stripping mechanism (300) which are sequentially arranged along the flow direction of the extractant; The multi-stage countercurrent extraction mechanism (100) comprises two or more groups of multi-stage extraction tanks arranged in parallel, each group of the multi-stage extraction tanks comprises a primary extraction tank (11), a secondary extraction tank (12), ..., an n-stage extraction tank (13) arranged in series, each of the n-stage extraction tanks (13) is respectively connected to a brine storage tank (102) to be extracted, and each of the primary extraction tanks (11) is respectively connected to an extractant storage tank (101); Each of the n-stage extraction tanks (13) is connected to the washing mechanism (200), a washing liquid input pipe is provided on a side of the washing mechanism (200) away from the extraction tank, and the side of the washing mechanism (200) away from the extraction tank is also connected to the stripping mechanism (300); A stripping liquid inlet pipe is provided on a side of the stripping mechanism (300) away from the washing mechanism (200), and a high-lithium liquid storage tank (302) is provided on a side of the stripping mechanism (300) close to the washing mechanism (200).

2. The system for extracting lithium from salt lakes according to claim 1, characterized in that: The washing mechanism (200) comprises at least a primary washing tank (21) and a secondary washing tank (22) which are arranged in series, the oil phase outlet of each of the n-stage extraction tanks (13) is connected to the oil phase inlet of the primary washing tank (21), the secondary washing tank (22) is connected to the washing liquid storage tank (201) via the washing liquid input pipe, and the oil phase outlet of the secondary washing tank (22) is connected to the stripping mechanism (300).

3. The system for extracting lithium from salt lakes according to claim 2, characterized in that: The water phase outlet of the primary washing tank (21) is respectively connected to the inlet of each of the n-stage extraction tanks (13), so that the residual liquid obtained from the primary washing tank (21) can be extracted again.

4. The system for extracting lithium from salt lakes according to claim 2, characterized in that: The stripping mechanism (300) comprises a primary stripping tank (31), a secondary stripping tank (32) and a tertiary stripping tank (33) which are sequentially connected in series, the primary stripping tank (31) being connected to a high lithium solution storage tank (302) and an oil phase outlet of the secondary washing tank (22) respectively, and the tertiary stripping tank (33) being connected to a stripping solution storage tank (301) via a stripping solution input pipe.

5. The system for extracting lithium from salt lakes according to claim 4, characterized in that: The oil phase outlet of the tertiary stripping tank (33) is connected to the extractant storage tank (101), so that the oil phase after stripping can be used again for the brine to be extracted.

6. The system for extracting lithium from salt lakes according to claim 1, characterized in that: Each of the primary extraction tanks (11) is also connected to a raffinate clarification tank (400), and the oil phase outlet of the raffinate clarification tank (400) is connected to the inlet of the extractant storage tank (101), so that the extractant remaining in the raffinate can be recovered.

7. The system for extracting lithium from salt lakes according to claim 6, characterized in that: The raffinate clarification tank (400) is also connected to a first oil separator (500).

8. The system for extracting lithium from salt lakes according to claim 1, characterized in that: The high-lithium liquid storage tank (302) is also connected to a second oil separator (600).

9. A method for extracting lithium from a salt lake using the system for extracting lithium from a salt lake according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1, the extract is respectively fed from each of the first-stage extraction tanks (11) into the multi-stage countercurrent extraction mechanism (100), the brine to be extracted is respectively fed from each of the n-stage extraction tanks (13) into the multi-stage countercurrent extraction mechanism (100), the raffinate discharged from each of the n-stage extraction tanks (13) is respectively fed into the extraction tank of the previous stage, and finally the raffinate is discharged from each of the first-stage extraction tanks (11), and each of the n-stage extraction tanks (13) obtains the extracted oil phase; S2, the extracted oil phase obtained in step S1 enters the washing mechanism (200), and is washed with a washing liquid to obtain a washed oil phase; S3. The washed oil phase obtained in step S2 enters the stripping mechanism (300) and is stripped using a stripping liquid to obtain a high-lithium solution.

10. The method for extracting lithium from a salt lake according to claim 9, characterized in that: In step S2, a washing residue is obtained after the washing, and the washing residue is returned to the n-stage extraction tank (13).

11. The method for extracting lithium from a salt lake according to claim 9, characterized in that: In step S3, an oil phase liquid is obtained after the stripping, and the oil phase liquid is returned to the extractant storage tank (101).

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